[Fix #525] and clojure-emacs/cider-nrepl#25, bencode parser can handle nil

Author: gtrak

nrepl-client.el

@@ -198,13 +198,15 @@ To be used for tooling calls (i.e. completion, eldoc, etc)")
         ((looking-at "l")
          (goto-char (match-end 0))
          (let (result item)
-           (while (setq item (nrepl-bdecode-buffer))
+           ;; check for the end sentinel, setq returns the value
+           (while (not (eq :end (setq item (nrepl-bdecode-buffer))))
              (setq result (cons item result)))
            (nreverse result)))
         ((looking-at "d")
          (goto-char (match-end 0))
          (let (dict key item)
-           (while (setq item (nrepl-bdecode-buffer))
+           ;; check for the end sentinel, setq returns the value
+           (while (not (eq :end (setq item (nrepl-bdecode-buffer))))
              (if key
                  (setq dict (cons (cons key item) dict)
                        key nil)
@@ -214,7 +216,12 @@ To be used for tooling calls (i.e. completion, eldoc, etc)")
            (cons 'dict (nreverse dict))))
         ((looking-at "e")
          (goto-char (match-end 0))
-         nil)
+         ;; This line used to return nil and checks above checked for
+         ;; falsiness to indicate the end of a list/dict, but that
+         ;; meant that nil/() was unable to pass through without
+         ;; shorting the algorithm. Now we return an :end keyword
+         ;; as a sentinel value and check for equality.
+         :end)
         (t
          (error "Cannot decode object: %d" (point)))))
 

test/nrepl-bencode-tests.el

@@ -90,3 +90,9 @@
                     ("status" "done")))
                  (nrepl-decode
                   "d2:id2:422:ns4:user7:session36:3f586403-ed47-4e4d-b8db-70522054f9715:value5:\"←\"ed2:id2:427:session36:3f586403-ed47-4e4d-b8db-70522054f9716:statusl4:doneee"))))
+
+(ert-deftest test-nrepl-decode-nils ()
+  (should (equal '(("" nil (dict ("" . nil))))
+                 (nrepl-decode "l0:led0:leee")))
+  (should (equal '(("" nil (dict ("" . 6))))
+                 (nrepl-decode "l0:led0:i6eee"))))